1. Field of the Invention
The present invention relates to a semiconductor silicon wafer used to manufacture a semiconductor integrated circuit (IC) (i.e. semiconductor silicon wafer for IC).
2. Description of the Related Art
FIG. 3 shows a semiconductor silicon wafer for IC having symmetrical beveled portions 21a and 21b formed on the front and back surfaces thereof.
The beveled portions 21a and 21b of the semiconductor silicon wafer 21 are arranged as follows. Assuming that the beveled portion 21a on the front surface has a beveled width w.sub.1 and a beveled depth d.sub.1, and the beveled portion 21b on the back surface thereof has a beveled width w.sub.2 and a beveled depth d.sub.2, w.sub.1 =w.sub.2, and d.sub.1 =d.sub.2, and the angle .theta..sub.1 between the inclining surface of the beveled portion 21a and the main surface on the front surface side [.theta..sub.1 =arc tan (d.sub.1 /w.sub.1)] is equal to the angle .theta..sub.2 between the inclining surface of the beveled portion 21b and the main surface on the back surface side [.theta..sub.2 =arc tan (d.sub.2 /w.sub.2)]. Note that, in this case, the beveled width w.sub.1 of the beveled portion 21a of the front surface and the beveled angle .theta..sub.1 of the front surface are set to such values that do not cause a crown along the wafer edge when photoresist is applied or an epitaxial layer is formed later on the front surface.
Nevertheless, the following problems arise in the above technology.
As described above, according to the above semiconductor silicon wafer 21, the beveled width w.sub.1 of the front beveled portion 21a is set to a width equal to or larger than a prescribed value and the front beveled angle .theta..sub.1 is set so that a crown is not formed in the application of photoresist or the subsequent formation of an epitaxial layer. Along with the above consideration, the equations w.sub.1 =w.sub.2 and d.sub.1 =d.sub.2 are observed and the beveling therefore is symmetrically effected on the front and back surfaces, and thus the beveling of the back surface gives an adverse effect of chipping due to too much beveling aside from the above-mentioned effect of the beveling of the front surface.
More specifically, when .theta..sub.1 has a small value, e.g., 20.degree. or less, the width of the remained outer circumference of the wafer is narrowed, in other words, the outer circumferential edge of the wafer has a sharp wedge-shaped cross section. As a result, a problem arises in that the semiconductor silicon wafer is liable to be chipped off in the following processing.